Specifications

Table Of Contents
APPENDIX E: INTEROPERABILITY
Page 212 MRC-565 Packet Data Radio Operations & Maintenance
FleetTrak
TM
The FleetTrak
TM
network is used for applications that require the position of mobile resources to
be reported in real-time and at varying update rates. A typical FleetTrak network is shown
below. One or more Data Centers are normally used for the central collection and distribution of
data to a customer’s office. The network can be as small as one base station or may be comprised
of thousands of base stations, repeaters and remote stations. The networks are used for position
reporting in mobile applications (AVL), fixed site data collection (SCADA) and messaging.
Either an MRC-565 or MRC-565C may be used in a FleetTrak
TM
network.
The FleetTrak
TM
network operates line-of-sight using groundwave. The range of communication
by groundwave is primarily determined by diffraction around the curvature of the earth,
atmospheric diffraction and tropospheric propagation. These ranges are successfully extended by
MRC from 50-100 miles through the use of robust protocols, sensitive receivers and short
packetized messages.
The FleetTrak
TM
network uses the ELOS protocol and combines CSMA (carrier sense multiple
access) and TDMA (time division multiple access) for achieving a channel utilization greater
than 90%.
When a remote station (mobile) desires to establish connectivity with the network it sends a “poll
request”, which specifies data type and desired update interval, to the nearest base station using
the CSMA mode. The base station acknowledges this request and adds the mobile to its TDMA
polling database. The mobile then sends its data in the TDMA mode when polled by the base
station.
Since one base station may be in contact with hundreds of mobiles at any one time, it organizes
the responses from up to 10 mobiles on a single transmission burst (TDMA). The ten mobiles